Yes, Bellsouth Customer Service is submerged in Yahoo. The bellsouth.net, pacbell.net, sbcglobal.net, att.net, and others are Yahoo, the company that AT&T pays to offer the email service. Consequently, if customers want to use their Bellsouth email account, then they are caught with Yahoo.
https://www.emailsupport-contact.net/bellsouth-email/